The present invention concerns a timepiece including a striking work mechanism. It relates to clocks, chronographs and other clockwork-movements. It concerns more particularly portable clockwork-movements, i.e. those that can be put in a pocket or attached to the wrist.
Timepieces that emit an acoustic signal at the end of a predetermined and adjustable time are already known. These timepieces conventionally include a clockwork-movement measuring in particular the time and a striking work whose triggering is controlled by the movement.
The timepieces of the aforecited type are designed for example for timing a limited parking time of a vehicle, and remind the user with ringing or a gong that the parking time has run out.
The timepiece according to the invention is intended amongst others, but not exclusively, for such an application.
A first category of timepieces concerns the clocks, alarm clocks and other wristwatches, which are provided with a striking work actuated by the same spring barrel as that which supplies the timekeeping device with mechanical energy. These mechanisms thus include a single spring, which, during a first operating period, operates the clockwork-movement, and during a second operating period, provides the energy necessary for the warning signal to operate. Such mechanisms are essentially characterised in that, between the moment of winding and setting the time and the moment that the alarm is triggered, the barrel drum actuates the clockwork-movement, whereas at the moment the alarm is triggered, one hammer is released, which strikes a gong of any appropriate type, said hammer then being actuated by the same barrel drum, but the clockwork-movement spring acting, owing to a special mechanism, via a detent movement in the opposite direction.
As will be easily understood, mechanisms of the type described hereinbefore are extremely complex and thus expensive to manufacture. They require a large number of special parts that are not available on the market and that therefore have to be made to measure. These mechanisms are also very fragile. Finally, since the same motor spring ensures both the working of the clockwork-movement and that of the striking work mechanism, the force of the spring is not used solely to measure the time, which limits the power reserve of the watch and requires its user to wind it regularly, and more often the more he uses the alarm device.
In order to overcome these drawbacks, a second type of watch has been proposed, fitted with a striking work actuated by an auxiliary barrel spring independent of the barrel spring supplying energy to the timekeeper. Surprisingly, it has been observed that addition, in a conventional clockwork-movement, of a second movement distinct from the first and reserved solely for the proper working of the alarm mechanism, was not accompanied by a prohibitive increase in manufacturing costs, insofar as such a mechanical construction allows the general kinematics of the clockwork movement to be substantially simplified.
Among the problems that remain to be resolved however, one concerns the triggering of the timer function and winding of the motor spring of the auxiliary barrel whose force is used to actuate the striking work. Indeed, to the Applicant's knowledge, the only technical solutions currently available consist of two distinct push-buttons, one of these push-buttons being used to actuate the countdown of time after the period at the end of which the warning signal has to be emitted has been selected, whereas the other push-button is used to wind the motor spring of the striking work. This multiplication of push buttons tends to increase the cost price of the timepiece and is detrimental to its aesthetic appearance.
According to a variant, the winding crown which, primitively, is for winding the single movement that measures the time, may also be used to wind the striking work. Such an arrangement, however, again considerably complicates the construction of the watch and, due to the use of special parts, which are not available on the market, that it involves, inevitably leads to a significant increase in manufacturing costs.
Another known solution for winding the motor spring used to drive the striking work consists in using a slide-bar, i.e. a mechanism which moves with friction in or on a slide way, accessible from outside the watchcase. The winding of the aforementioned motor spring results from actuation of the slide-bar whose movement is transmitted to a rack meshing with the wheel of the shaft that supports the barrel to which said motor spring is hooked. The slide-bar is conventionally acted upon by a bolt that is manoeuvred with a finger and which is used to wind the striking work motor spring. Such a device practically is no longer used at the present time since, unless particularly complex and thus expensive measures are taken, it irreparably damages the water resistance of the watchcase to which it is fitted.